Tips for installing 4-1 headers

chickenStripCharlie

Coast to Coast
Anyone have tips on installing 4-1 headers for the first time?

Doing it on a 83 cb750 sc (nighthawk) (with mac 4-1 exhaust off a '82 cb750c) and I simply do not have enough room between the header pipe and frame rails to get the collars to slide up .

I'm sure there is a sequence to follow to make it easier, but I'm not seeing it.

I mean the claearance between 1-2 and 3-4 is barely enough to go around the frame rail on each side *shrug*

Appreciate the advice
 

chickenStripCharlie

Coast to Coast
Here is the header. My research shows it to be MAC 4-1 exhaust.

20200419_170633.jpg


As far as I remember the frame on the cb750 and nighthawk should be identical.
Here is the frame all f**** up now from multiple failed attempts

20200419_170647.jpg


Here is one side with the collar slipped on. Notice that the other side has about 1/8" space left only between it and the frame.

20200419_170454.jpg


Without collars or split collars the header does fit properly into the exhaust ports
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
In my experience, you can usually get the split collars under the flanges after you slide the flanges slightly over the studs. Also, make sure you have the flanges match their cylinder. With earlier CB750s, as well as CB650s, and CB550s, the inner flanges are not the same as the outer flanges and they have a particular orientation.
 

chickenStripCharlie

Coast to Coast
In my experience, you can usually get the split collars under the flanges after you slide the flanges slightly over the studs. Also, make sure you have the flanges match their cylinder. With earlier CB750s, as well as CB650s, and CB550s, the inner flanges are not the same as the outer flanges and they have a particular orientation.


Ok I will go check if flanges are all the same or different. Hadn't noticed before.

The donor 1982 CB750c is long gone, but I kept the engine. I looked, and seems exactly the same so exhaust should definitely fit. I'm the one that even removed it and cant remember it being too difficult.

Will try getting all flanges up, then working the split collars in. Thanks for the tip.
 

wozza

Been Around the Block
The wrap maybe to thick, as they can be tight fit near the frame rails even without wrap...also use rubber bands on the split collars to hold them in place makes it heaps easier, they will shoot off or melt on first run :)
 

chickenStripCharlie

Coast to Coast
Guys! Thanks for the tips!!!!!!!!!

I got it done with irk millers tip to go flanges first, then wiggle the split collars under.

It was tight but doable :)


Excuse the two-tone exhaust wrap. I ran out of the titanium. Not going for Bike of the month here lol. (Likely will remove a couple inches of the black wrap)

Still not happy about the paint damage though
20200419_202308.jpg


20200419_202259.jpg
 
Last edited:

Sderbyshire

Into Sailing, classic Triumph cars and motorbikes.
In my experience, you can usually get the split collars under the flanges after you slide the flanges slightly over the studs. Also, make sure you have the flanges match their cylinder. With earlier CB750s, as well as CB650s, and CB550s, the inner flanges are not the same as the outer flanges and they have a particular orientation.
That’s interesting Irk

when i refitted my original cb550f 4 into 1 i did not notice any difference in flanges, giess i’d better take it off again to check!

steve
 

chickenStripCharlie

Coast to Coast
That’s interesting Irk

when i refitted my original cb550f 4 into 1 i did not notice any difference in flanges, giess i’d better take it off again to check!

steve

On mine the flanges were all the same, but they had a L/R orientation. One side was just slightly lower profile and easier to maneuver around the frame rails.
 

irk miller

You've been mostly-dead all day.
DTT BOTM WINNER
That may be what I was thinking of, that the orientation is what is different. I don't remember flatter sides on my outer flanges on either my SOHC 750 or SOHC CB650 engine.
 

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